JPH10289728A - Alkaline secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkaline secondary battery which keeps high capacity for a long period. SOLUTION: An alkaline secondary battery furnishes an electrode group housed in a container 1 of a cylindrical form with bottom, and manufactured by providing separators 3 between positive electrodes 2 and negative electrodes 4, and winding in a spiral form and an alkaline electrolyte housed in the container 1. At least one side electrodes of the positive and the negative electrodes 2 and 4 are made in a structure holding an electrode material, including an active material and a hydrophilic binder to a collector. When the inner diameter of the container 1 is made A (mm), the diameter of the electrode group before housing to the container 1 is made B (mm), the apparent density of the separator 3 before the electrode group is manufactured is made C (g/cc), and that after being housed in the container is made D (g/cc), the above electrode group is made in a structure to satisfy the formula (0.90<=B/A<=1.05), and the formula (1.0<=D/C<=1.4).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an alkaline secondary battery, and more particularly to an alkaline secondary battery having an improved electrode group.

[0002]

2. Description of the Related Art Nickel cadmium secondary batteries and nickel hydrogen secondary batteries are known as alkaline secondary batteries. The battery structure of this secondary battery includes a cylindrical structure in which an electrode group produced by spirally winding a positive electrode and a negative electrode via a separator is housed in a cylindrical container having a bottom, and a positive electrode and a negative electrode. Is known in which a group of electrodes produced by laminating the electrodes via a separator is housed in a bottomed rectangular cylindrical container.

In such an alkaline secondary battery,
Paste electrodes are widely used for the positive electrode and the negative electrode because they can be relatively easily manufactured and the manufacturing cost is low. For example, paste-type cadmium electrodes are usually
To cadmium oxide powder or cadmium hydroxide powder as an active material, a reinforcing fiber for imparting electrode strength and a thickener for binding these are added, and kneaded together with ethylene glycol as a solvent to form an active material paste. Is prepared, and the paste is applied to the surface of the conductive core body, dried, subjected to a chemical conversion treatment if necessary, and cut into a desired size. As the thickener, a hydrophilic thickener such as sodium polyacrylate or carboxymethyl cellulose is used.

However, in an alkaline secondary battery having the cadmium electrode as a negative electrode, the electrolyte in the separator moves to the hydrophilic thickener of the negative electrode as the charge / discharge cycle proceeds, and the thickener swells. As a result, the adhesion between the active material and the conductive core in the negative electrode is reduced, and the conduction between the active material and the conductive core is reduced, so that there is a problem that the discharge capacity is reduced.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide, as a positive electrode and / or a negative electrode, a current collector on which an electrode material containing an active material and a hydrophilic binder is carried, and the charge and discharge cycle proceeds. An object of the present invention is to provide a high-capacity alkaline secondary battery in which swelling of the binder is suppressed and which has a high capacity for a long period of time.

[0006]

The alkaline secondary battery according to the present invention is a spirally wound cylindrical container having a bottomed cylindrical shape, which is housed in the container and has a separator interposed between a positive electrode and a negative electrode. An electrode group produced by the above, an alkaline electrolyte contained in the container, and a sealing member disposed at an opening of the container, and at least one electrode of the positive electrode and the negative electrode is Having a structure in which an electrode material containing an active material and a hydrophilic binder is supported on a current collector, the inner diameter of the container is A (mm), and the diameter of an electrode group before being housed in the container Is B (mm), the halo density of the separator is C (g / cc) before preparation of the electrode group, and D (g / cc) after storage in the container. Equation and the following equation (2) 0.90 ≦ B / A ≦ 1.05 (1) 1.0 ≦ D / It is characterized in that it has ≦ 1.4 a structure satisfying (2).

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an alkaline secondary battery (cylindrical alkaline secondary battery) of the present invention will be described with reference to FIG. A positive electrode 2 and a separator 3 are placed in a cylindrical container 1 having a bottom.
And a negative electrode 4 are stacked and spirally wound to house an electrode group 5. The negative electrode 4
Are arranged at the outermost periphery of the electrode group 5 and are in electrical contact with the container 1. The alkaline electrolyte is contained in the container 1. A circular first sealing plate 7 having a hole 6 in the center is arranged at the upper opening of the container 1.
The ring-shaped insulating gasket 8 is disposed between the peripheral edge of the sealing plate 7 and the inner surface of the upper opening of the container 1, and the container 1 is formed by caulking to reduce the diameter of the upper opening inward.
The sealing plate 7 is hermetically fixed via the gasket 8. One end of the positive electrode lead 9 is connected to the positive electrode 2,
The other end is connected to the lower surface of the sealing plate 7. The positive electrode terminal 10 having a hat shape is attached on the sealing plate 7 so as to cover the hole 6. The rubber safety valve 11
The hole 6 is disposed in a space surrounded by the sealing plate 7 and the positive electrode terminal 10 so as to close the hole 6. The circular pressing plate 12 made of an insulating material having a hole in the center is
The projecting portion of the positive electrode terminal 10 is disposed on the reference numeral 0 so as to project from the hole of the holding plate 12. The outer tube 13 covers the periphery of the holding plate 12, the side surface of the container 1, and the periphery of the bottom of the container 1.

The electrode group 5 has an inner diameter of the container 1 of A
(Mm), the diameter of the electrode group 5 (before being housed in the container 1) is B (mm), the halo density of the separator 3 is C (g / cc) before the electrode group is prepared, Container 1
When D (g / cc) is stored in
It has a structure that satisfies the expression and the expression (2).

0.90 ≦ B / A ≦ 1.05 (1) 1.0 ≦ D / C ≦ 1.4 (2) Here, the diameter B (mm) is obtained from the following equation (I). .

B = R + (T _p × N _p + T _n × N _n + T _s × N _s ) (I) In the above formula (I), R is the diameter (mm) of the winding core, T _p
Is the thickness of the positive electrode (mm), _Tn is the thickness of the negative electrode (mm), T
_s The thickness of the separator (mm), N _p is positive number diameter line of the electrode group is maximum bondage degree, N _n is the number of the negative diameter line of the electrode group is maximum bondage degree, N _s is the The number of separators on the diameter line at which the electrode group has the maximum degree of binding is shown. The thickness of the positive electrode (T _p ), the thickness of the negative electrode (T _n ), and the thickness of the separator (T _s ) in the electrode group are each measured by a micrometer having a pressure of 5 kg / cm ² .

Further, the halo density C (g / cc) of the strip-shaped separator before forming the electrode group can be obtained from the following equation (II). C = (1000 × W) / (T _s × S) (II) where W is the weight (g) of the separator,
Indicates the area (mm ² ) of the separator.

The halo density D (g / cc) of the separator of the electrode group (without impregnation of the electrolyte) accommodated in the container is measured by the method described below. That is, the electrode group is cut along a direction orthogonal to the winding direction, and the obtained cut surface is magnified 100 times with a magnifying microscope. The thickness (T _s ′) of the separator in this enlarged view was measured, and the following (II)
The halo density D obtained by the equation (I) is obtained.

D = (1000 × W) / (T _s ′ × S) (II) B / A is the degree of binding of the electrode group. The reason for limiting the degree of binding to the above range is as follows. When the degree of binding is less than 0.90, it becomes difficult to secure an appropriate amount of voids in the separator, so that the hydrophilic binder contained in the positive electrode and / or the negative electrode accompanying the progress of the charge / discharge cycle is reduced. It becomes difficult to suppress swelling, and the discharge capacity of the secondary battery decreases. On the other hand, the degree of binding is 1.
When it exceeds 05, when the electrode group is housed in the container, a member (for example, a negative electrode) located on the outer periphery of the electrode group is damaged by contact with the container. Further, when the member located on the outer periphery of the electrode group is a positive electrode or a negative electrode, the active material falls off due to breakage, resulting in a decrease in capacity and an internal short circuit. A more preferred degree of tightening is in the range of 0.98 to 1.05.

The reason for limiting the D / C to the above range is as follows. When the D / C is less than 1.0, the voids in the separator decrease, and the amount of the electrolyte that can be retained in the separator decreases, so that the hydrophilic binder contained in the positive electrode and / or the negative electrode as the charge / discharge cycle progresses. It becomes difficult to suppress the swelling of the adhesive. On the other hand, the D /
When C exceeds 1.4, the ratio of the separator in the electrode group increases, and the ratio of the positive electrode and the negative electrode in the electrode group decreases. Accordingly, the battery capacity may decrease. More preferred D / C is in the range of 1.0 to 1.2.

Next, the positive electrode 2, the negative electrode 4, the separator 3
And the electrolyte will be described. 1) Positive Electrode 2 The positive electrode 2 is formed from a positive electrode material containing nickel hydroxide particles and a binder supported on a current collector.

As the nickel hydroxide particles, for example, single nickel hydroxide particles or nickel hydroxide particles in which zinc and / or cobalt are coprecipitated with metallic nickel can be used. The latter positive electrode containing nickel hydroxide particles can further improve the charging efficiency in a high temperature state.

From the viewpoint of improving the charging / discharging efficiency of the alkaline storage battery, the peak half-value width of the (101) plane of the nickel hydroxide particles by X-ray powder diffraction method is 0.8 ° / 2θ.
(Cu-Kα) or more is preferable. A more preferable nickel hydroxide powder is powder X-ray diffraction method (10
1) The half width of the surface peak is 0.9 to 1.0 ° / 2θ.
(Cu-Kα).

Examples of the binder include polytetrafluoroethylene (PTFE), polyethylene, polypropylene, rubber-based polymers (eg, styrene butadiene rubber (SBR) latex, acrylonitrile butadiene rubber (NBR) latex, ethylene propylene Hydrophobic polymers such as diene monomers (latex of EPDM); carboxymethyl cellulose (CM
C), methylcellulose (MC), hydroxypropylmethylcellulose (HPMC), polyacrylate (eg, sodium polyacrylate (SPA)), polyvinyl alcohol (PVA), polyethylene oxide, CO
A hydrophilic polymer such as a copolymer of a monomer having at least one OX group with vinyl alcohol (where X is an element selected from hydrogen, alkali metal and alkaline earth metal); and the like. As the binder, one or more kinds selected from the above-mentioned polymers can be used. Further, a mixed polymer composed of the hydrophobic polymer and the hydrophilic polymer is preferably used. Among them, polytetrafluoroethylene (PTF
E), carboxymethylcellulose (CMC), hydroxypropylmethylcellulose (HPMC), and polyacrylate are preferred. In addition, the polyethylene, the polypropylene, and the polytetrafluoroethylene can be used in the form of a dispersion.

Examples of the current collector include those having a sponge-like, fibrous, or felt-like porous structure made of a metal such as nickel or stainless steel or a nickel-plated resin.

For the positive electrode, for example, a paste containing nickel hydroxide particles, cobalt-based particles as a conductive additive, a binder, and water is prepared, and the paste is filled in a current collector, which is dried and heated. After pressing, the resultant is cut into a desired size to produce a positive electrode having a structure in which a positive electrode material containing nickel hydroxide particles and a binder is supported on a current collector.

As the cobalt compound forming the cobalt-based particles, for example, dicobalt trioxide (Co ₂ O)
₃ ), cobalt metal (Co), cobalt monoxide (Co)
O), cobalt hydroxide {Co (OH) ₂ } and the like.

2) Negative Electrode 4 The negative electrode 4 is formed of a negative electrode material containing a negative electrode active material and a binder carried on a current collector.

Examples of the negative electrode active material include cadmium compounds such as metal cadmium and cadmium hydroxide, and hydrogen. Examples of the host matrix of hydrogen include a hydrogen storage alloy.

Above all, the hydrogen storage alloy is preferable because the capacity of the secondary battery can be improved as compared with the case where the cadmium compound is used. The hydrogen storage alloy is not particularly limited, and may be any as long as it can store hydrogen electrochemically generated in an electrolytic solution and can easily release the stored hydrogen during discharge. For example, LaNi ₅ , Mm
Ni ₅ (Mm is a misch metal), LmNi ₅ (Lm is at least one selected from rare earth elements including La),
A part of Ni of these alloys is Al, Mn, Co, Ti, C
Examples thereof include a multi-element-based material substituted with an element such as u, Zn, Zr, Cr, and B, or a TiNi-based or TiFe-based material. In particular, the general formula LmNi _w Co _x Mn
_y Al _z (the total value of atomic ratios w, x, y, and z is 5.00 ≦
(W + x + y + z ≦ 5.50) The hydrogen storage alloy having the composition represented by the formula (1) is suitable because it can suppress the pulverization accompanying the progress of the charge / discharge cycle and improve the charge / discharge cycle life.

As the binder, one or more selected from the same polymers as those described for the positive electrode can be used. Among them, it is preferable to use polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), polyacrylate, and polyvinyl alcohol (PVA).

As the current collector, for example, a two-dimensional substrate such as a punched metal, an expanded metal, a perforated rigid plate, a nickel net, or a three-dimensional substrate such as a felt-like metal porous material or a sponge-like metal porous material is used. Can be mentioned.

This negative electrode 4 is formed, for example, by the negative electrode active material,
The paste is prepared by kneading the conductive material and the binder together with water to prepare a paste, filling the paste into the conductive substrate, drying, and then molding.

Examples of the conductive material include carbon black and graphite. 3) Separator 3 Examples of the separator 3 include a nonwoven fabric made of a polyamide fiber and a nonwoven fabric made of a polyolefin fiber such as polyethylene and polypropylene provided with a hydrophilic functional group.

4) Alkaline Electrolyte As the alkaline electrolyte, for example, an aqueous solution of sodium hydroxide (NaOH), lithium hydroxide (LiOH)
Aqueous solution, potassium hydroxide (KOH) aqueous solution, NaO
H and LiOH mixed solution, KOH and LiOH mixed solution, K
A mixed solution of OH, LiOH, and NaOH can be used.

The electrode group provided in the alkaline secondary battery according to the present invention has a separator between a positive electrode and a negative electrode,
It is manufactured by spirally winding, and at least one of the positive electrode and the negative electrode has a structure in which an electrode material containing an active material and a hydrophilic binder is supported on a current collector, and a degree of tightness ( B / A) is in the range of 0.90 to 1.05,
In addition, the halo density of the separator is determined by the equation (2) (1.
0 ≦ D / C ≦ 1.4). In such a secondary battery, an appropriate amount of voids can be left in the separator of the electrode group, so that the electrolyte retention of the separator can be improved. As a result, since the separator can hold a sufficient amount of electrolyte for a long period of time, the electrolyte in the separator is included in the positive electrode and / or the negative electrode as the charge and discharge cycle proceeds. The migration to the hydrophilic binder can be suppressed or avoided. For this reason, in the positive electrode and the negative electrode, the adhesiveness between the active material and the current collector is reduced due to the swelling of the binder, and conduction between the active material and between the active material and the current collector is deteriorated, The falling off of the active material can be suppressed or avoided. Further, when the negative electrode is formed from a material in which an electrode material including a hydrogen storage alloy and a hydrophilic binder is supported on a current collector, the hydrogen storage alloy which is generated by repetition of charge and discharge is dropped due to pulverization. Also, floating of the finely divided hydrogen storage alloy in the electrolyte can be suppressed or prevented. Therefore, the secondary battery can maintain a high capacity for a long period of time.

In the secondary battery, since the electrolyte in the separator can be prevented from being depleted, an increase in internal resistance can be suppressed, and excellent charge and discharge efficiency can be obtained over a long period of time. High discharge voltage can be maintained.

[0032]

【Example】

Example 1 <Preparation of Positive Electrode> 0.3 part by weight of carboxymethyl cellulose (hydrophilic binder) was added to a mixed powder composed of 90 parts by weight of nickel hydroxide powder and 10 parts by weight of cobalt monoxide powder as a conductive aid. 0.5 parts by weight of polytetrafluoroethylene was added, and 45 parts by weight of water was further added to the mixture and kneaded to prepare a paste. After filling this paste into a sintered fiber substrate as a current collector and drying,
A positive electrode having a structure in which a positive electrode material containing nickel hydroxide particles and a hydrophilic binder was supported on a current collector was manufactured by roller pressing and rolling. <Preparation of Negative Electrode> A hydrogen storage alloy having a composition of LmNi _4.0 Co _0.4 Mn _0.3 Al _0.3 was prepared using a commercially available lanthanum-enriched misch metal Lm, Ni, Co, Mn and Al in a high frequency furnace. The hydrogen storage alloy was mechanically pulverized and passed through a 200-mesh sieve. To 100 parts by weight of the obtained alloy powder, 0.5 parts by weight of sodium polyacrylate and 0.125 parts by weight of carboxymethylcellulose as a hydrophilic binder, and a dispersion of polytetrafluoroethylene (specific gravity 1.5, solid content 60 parts by weight) %) 2.5 parts by weight and 1.0 part by weight of carbon powder as a conductive material were added, and mixed with 50 parts by weight of water to prepare a paste. This paste was applied to a punched metal, dried, and then subjected to pressure molding to produce a negative electrode having a structure in which a negative electrode material containing a hydrogen storage alloy and a hydrophilic binder was supported on a current collector.

Next, an acrylic acid monomer was graft-copolymerized on a polypropylene
mm × 45mm size, 60g / m ²
Thus, a separator having a thickness of 0.20 mm was produced. The halo density C of the separator was 0.3 g / cc as determined from the above-mentioned equation (II). The separator was interposed between the positive electrode and the negative electrode and spirally wound to form an electrode group. When the thicknesses of the positive electrode, the negative electrode and the separator of the electrode group were measured by the aforementioned micrometer with a pressure of 5 kg / cm ² , the thickness T _{p of the} positive electrode was 0.63 mm.
In thickness T _n of the negative electrode is 0.27 mm, the thickness T _s of the separator was 0.20 mm. The diameter of the core used for producing the electrode group was 3.0 mm.
Six positive number N _p is on a diameter line which the electrode group is maximum bondage degree, negative number N _n is 8 sheets, separators number N _s was 15 sheets. Formula (I) described above; B = R +
Was determined the diameter of the electrode group by _{(T p × N p + T} n × N n + T s × N s), was 11.9 mm.
After storing such an electrode group in a bottomed cylindrical container having an inner diameter A of 13.3 mm, 7N KOH and 1
AA size (theoretical capacity: 12) containing an alkaline electrolyte composed of N LiOH and having the structure shown in FIG.
(00 mAh) was assembled.

The degree of tightness of the electrode group of such a secondary battery (B
/ A) is 0.90. The halo density D (g / cc) of the separator of the electrode group housed in the container was determined by the following method. That is, an electrode group having the same configuration as described above was housed in a container having the same shape as described above. At this time, no electrolyte is contained in the container. This container was cut along a direction orthogonal to the winding direction of the electrode group, and the cut surface obtained was magnified 100 times with a magnifying microscope. The thickness of the separator in this enlarged view was measured. Using the obtained thickness, the halo density D was calculated from the above-mentioned equation (III) to obtain 0.3 (g / cc). Accordingly, the halo density C (g / cc) of the separator before winding and the halo density D (g / c) of the separator of the electrode group housed in the container.
The ratio (D / C) to c) is 1.0. (Example 2) the electrode group by changing the diameter of the core 3.3 mm, the positive electrode thickness T _p of the front electrode group housed in the container 0.64 mm, the FukyokuAtsu of T _n to 0.31mm Example 1 except that the degree of binding (B / A) was 0.95.
The same nickel-metal hydride secondary battery was manufactured. The capacity ratio between the positive electrode and the negative electrode was set to be the same as in Example 1 as much as possible. (Example 3) electrode groups by changing the diameter of the core 3.8 mm, the positive electrode thickness T _p of the front electrode group housed in the container 0.65 mm, the FukyokuAtsu of T _n to 0.33mm Example 1 except that the degree of binding (B / A) was set to 1.00.
The same nickel-metal hydride secondary battery was manufactured. The capacity ratio between the positive electrode and the negative electrode was set to be the same as in Example 1 as much as possible. (Example 4) electrode groups by changing the diameter of the core 4.2 mm, the positive electrode thickness T _p of the front electrode group housed in the container 0.66 mm, the FukyokuAtsu of T _n to 0.35mm Example 1 except that the degree of binding (B / A) was 1.05.
The same nickel-metal hydride secondary battery was manufactured. The capacity ratio between the positive electrode and the negative electrode was set to be the same as in Example 1 as much as possible. (Comparative Example 1) electrodes by changing the diameter of the core 3.0 mm, the positive electrode thickness T _p of the front electrode group housed in the container 0.61 mm, the FukyokuAtsu of T _n to 0.26mm Example 1 except that the degree of binding (B / A) was 0.85.
The same nickel-metal hydride secondary battery was manufactured. The capacity ratio between the positive electrode and the negative electrode was set to be the same as in Example 1 as much as possible. (Comparative Example 2) electrode groups by changing the diameter of the core 4.5 mm, the positive electrode thickness T _p of the front electrode group housed in the container 0.66 mm, the FukyokuAtsu of T _n to 0.44mm And the ratio (D / g) between the halo density C (g / cc) of the separator before winding and the halo density D (g / cc) of the separator of the electrode group in the container is set to 1.10. A nickel-metal hydride secondary battery similar to that of Example 1 was manufactured except that / C) was changed to 1.8. The capacity ratio between the positive electrode and the negative electrode was set to be the same as in Example 1 as much as possible.

With respect to the obtained secondary batteries of Examples 1 to 4 and Comparative Examples 1 and 2, the battery was charged at 25 ° C. with a current of 1 C for 75 minutes, and then discharged at a current of 1 C to 1.0 V. The discharge capacity was measured repeatedly for each cycle, and the results are shown in FIG.

With respect to the secondary batteries of Examples 1 to 4 and Comparative Examples 1 and 2, the number of batteries (out of 100) where a leak failure occurred during the production of the electrode group was examined. The results are shown in Table 1 below. Table 1 Number of leak defects in 100 pieces (pieces) Example 10 Example 2 0 Example 3 1 Example 4 2 Comparative example 10 Comparative example 2 6 As is clear from FIG. 2, the degree of binding (B / A) ) Is 0.90
In the range of 1.0 to 1.05, the ratio (D / C) of the halo density C of the separator before preparing the electrode group to the halo density D of the separator of the electrode group in the container is in the range of 1.0 to 1.4. Examples 1-4
It can be seen that the secondary battery of No. has a longer charge / discharge cycle life than the secondary battery of Comparative Example 1 including an electrode group having a degree of binding smaller than the above range.

As is evident from Table 1, the secondary batteries of Examples 1 to 4 can reduce the number of leak defects during the production of the electrode group as compared with Comparative Example 2. The reason for the large number of leak failures in Comparative Example 2 is that the degree of tightness exceeds the above range. Some of the secondary batteries of Comparative Example 2 had the outermost periphery of the electrode group damaged.

[0038]

As described above in detail, according to the present invention, a high capacity and long life alkaline secondary battery can be provided.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing an alkaline secondary battery (cylindrical alkaline secondary battery) according to the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a charge / discharge cycle and a discharge capacity in Examples 1 to 4 and Comparative Examples 1 and 2 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Container, 2 ... Positive electrode, 3 ... Separator, 4 ... Negative electrode, 5 ... Electrode group, 7 ... Sealing plate.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Toshiharu Yuzukien 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Corporation

Claims (1)

[Claims] 1. A container having a bottomed cylindrical shape, an electrode group housed in the container, and spirally wound with a separator interposed between a positive electrode and a negative electrode, and It comprises a contained alkaline electrolyte, and a sealing member disposed at an opening of the container, wherein at least one electrode of the positive electrode and the negative electrode is
It has a structure in which an electrode material containing an active material and a hydrophilic binder is supported on a current collector, the inner diameter of the container is A (mm), and the diameter of the electrode group before being housed in the container is B (mm), the halo density of the separator was C (g / cc) before preparing the electrode group, and D (g / cc) after the container was housed. And an alkaline secondary battery having a structure satisfying the following equation (2): 0.90 ≦ B / A ≦ 1.05 (1) 1.0 ≦ D / C ≦ 1.4 (2)